Does sensitivity to interaural correlation changes correlate with binaural fusion performance?

Abstract

The purpose of this study was to assess whether and to what degree sensitivity to changes in interaural correlation (IC) in bilateral cochlear implant (CI) listeners is related to the overall degree of binaural fusion those listeners experience. Compared to typical-hearing listeners, CI users often report perceiving a reduced degree of binaural fusion. Because IC is a strong determiner of perceived fusion, degraded perception of fusion might be coupled with a relative insensitivity to changes in IC. To investigate this, two experiments were conducted. First, discrimination of IC changes was measured using the method of constant stimuli in which CI listeners identified the “target” interval containing an IC differing from the “reference” values of either 0.7 or 1.0. Stimuli were generated by modulating 1-kHz pulse trains by speech-derived envelopes the IC of which were manipulated. The same stimuli were used in a second procedure in which the perceived degree of fusion was quantified for ICs varying between 0.4–1.0. Preliminary results from both studies suggest that relative insensitivity to changes in IC are associated with a lesser degree of perceived fusion, overall.